Heat sink and communications product

ABSTRACT

A heat sink includes a base and a plurality of fins. A root of the fin is connected to the base. A heated area, a dropping pipe, and a spacing strip between the heated area and the dropping pipe are formed in the fin. A first passage and a second passage are formed between the heated area and the dropping pipe. A hydraulic diameter of a pipeline in the heated area is less than a critical dimension. A hydraulic diameter of a pipeline of the dropping pipe is greater than or equal to the critical dimension, and a pressure of liquid at an intersection of the second passage and the dropping pipe is greater than a pressure of liquid at an intersection of the second passage and the heated area.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/458,711, filed on Jul. 1, 2019, which is a continuation ofInternational Application No. PCT/CN2017/118641, filed on Dec. 26, 2017,The International Application claims priority to Chinese PatentApplication No. 201611260377.6, filed on Dec. 30, 2016. All of theafore-mentioned patent applications are hereby incorporated by referencein their entireties.

TECHNICAL FIELD

The present disclosure relates to the field of communicationstechnologies, and in particular, to a heat sink and a communicationsproduct to which the heat sink is applied.

BACKGROUND

A wireless module is widely applied in the field of communicationstechnologies. The wireless module is disposed in a communicationsproduct to implement signal transmitting and receiving. The wirelessmodule generates heat in a working process, and a heat sink is disposedto provide the wireless module with heat dissipation. An existing heatsink includes a base and a heat sink fin that is formed on the base. Asheat consumption of the wireless module gradually increases, a height ofthe heat sink fin needs to be continuously increased when a length and awidth of the heat sink are fixed. However, heat dissipation efficiencyof the heat sink fin gradually decreases as the height of the heat sinkfin is increased, causing a mismatch between an increase in an overallheat dissipation capability and an increase in weight.

Therefore, a heat sink with high heat dissipation efficiency is a focusof follow-up research.

SUMMARY

Embodiments of the present disclosure provide a heat sink with high heatdissipation efficiency and a communications product using the heat sink.

According to a first aspect, the present disclosure provides a heatsink, including a base and a plurality of fins, where the plurality offins are disposed on the base to form a cooling fin structure, and eachof the fins includes a root and a tip that are disposed opposite to eachother. The root is connected to the base, and the tip is located on aside, far away from the base, of the fin. In an embodiment, the fin iserected on a surface of the base by combining the root and the base. Thefin and the base may be perpendicular to each other, or there may be aspecific tilt angle between the fin and the base. A standard for settingthe tilt angle is to ensure that the tip far away from the base reachesa temperature making a working medium in the fin turn from a gas stateto a liquid state. A heated area, a dropping pipe, and a spacing stripthat separates the heated area from the dropping pipe are formed in thefin. The heated area is located between the root and the spacing strip.The dropping pipe is located between the spacing strip and the tip. Afirst passage and a second passage are formed between the heated areaand the dropping pipe. A hydraulic diameter of a pipeline in the heatedarea is less than a critical dimension such that the working medium inthe heated area is heated to form a gas-liquid plug flow flowing towardthe first passage and flowing into the dropping pipe through the firstpassage. A hydraulic diameter of the dropping pipe is greater than orequal to the critical dimension, and a pressure of liquid at anintersection of the second passage and the dropping pipe is greater thana pressure of liquid at an intersection of the second passage and theheated area such that liquid in the dropping pipe flows toward theheated area through the second passage.

The hydraulic diameter is a ratio of four times a flow cross-sectionalarea to a wetted perimeter. The critical dimension is a maximumhydraulic diameter of a pipeline that can be used when the workingmedium in the heated area is heated in the pipeline to form a gas-liquidplug flow. In other words, when the hydraulic diameter of the pipelineis greater than the critical dimension, the working medium heated in thepipeline cannot become in the gas-liquid plug flow state. A requiredhydraulic diameter of the pipeline varies according to different workingmedia.

In the present disclosure, the pipeline in the heated area and thedropping pipe are formed in the fin, the heated area and the droppingpipe are isolated from each other by the spacing strip, and the firstpassage and the second passage are disposed at two ends of the spacingstrip such that the heated area and the dropping pipe are communicatedwith each other. Because the base is close to a heat source, the workingmedium in the heated area is heated. In addition, because the hydraulicdiameter of the pipeline in the heated area is less than the criticaldimension, the working medium can form the gas-liquid plug flow afterbeing heated. Air bubbles in the liquid push the liquid to flow towardthe first passage at a top. The first passage is equivalent to atransverse flow gathering area at the top of the fin. Because the airbubbles in the heated area rush up, liquid reaching the first passagedoes not flow downward but flows along the first passage into thedropping pipe. The hydraulic diameter of the dropping pipe is greaterthan or equal to the critical dimension. The pressure of the liquid atthe intersection of the second passage and the dropping pipe is greaterthan the pressure of the liquid at the intersection of the secondpassage and the heated area such that the liquid in the dropping pipeflows toward the heated area through the second passage. In this way,the working medium inside the fin is circulated from the heated area tothe first passage, the dropping pipe, and the second passage, and thenback to the heated area.

In the present disclosure, a size of the pipeline in the heated area ofthe heat sink is restricted, that is, the hydraulic diameter of thepipeline in the heated area is less than the critical dimension suchthat the working medium in the heated area is heated to form thegas-liquid plug flow. In addition, a size of a pipeline of the droppingpipe is restricted. In other words, the hydraulic diameter of thedropping pipe is greater than or equal to the critical dimension. Inthis way, self-circulation is formed inside the fin of the heat sinksuch that the gas-liquid plug flow drives more liquid working media toparticipate in heat exchange, thereby improving heat dissipationefficiency.

In an implementation, the pipeline in the heated area includes aplurality of longitudinal pipelines and a transverse pipeline that iscommunicated between the plurality of longitudinal pipelines, thelongitudinal pipelines extend in a direction from the second passage tothe first passage, and the transverse pipeline is configured to performpressure balancing and temperature balancing of liquid and vapor.

In an implementation, the heated area includes a plurality of spacingzones, and each of the spacing zones separates the heated area to formthe longitudinal pipelines and the transverse pipeline. The spacingzones may be in a shape of a polygon (for example, hexagons or octagons)or circle.

In an implementation, the plurality of spacing zones are arranged in twocolumns, and the two columns of spacing zones are interlaced. In ahorizontal direction, a pipeline between two spacing zones in one columnis disposed opposite to a pipeline between two spacing zones in theother column. The two columns of spacing zones form three longitudinalpipelines.

In an implementation, the longitudinal pipeline extends in a shape of awave line.

In an implementation, a side, adjacent to the heated area, of thespacing strip is in a shape of a wave line, and a side, adjacent to thedropping pipe, of the spacing strip is straight-lined.

In an implementation, each of the spacing zones is bar-shaped, each ofthe spacing zones includes two straight-lined long sides, the two longsides are connected by curved sides, the spacing zones are arranged intwo columns, the longitudinal pipeline is formed between two adjacentcolumns of spacing zones, and the transverse pipeline is formed betweentwo adjacent spacing zones in one column.

In an implementation, both the side, adjacent to the heated area, of thespacing strip and the side, adjacent to the dropping pipe, of thespacing strip are straight-lined.

In an implementation, there are at least two columns of dropping pipes,and the dropping pipes in two adjacent columns are communicated witheach other through a transverse pipeline.

In an implementation, the first passage is honeycombed, and the firstpassage includes at least two crisscrossed pipelines.

In an implementation, a range of the critical dimension is 0.5 mm to 20mm. Selection of the critical dimension is associated with selection ofthe working medium.

In an implementation, the pipeline in the heated area of the fin and thepipeline of the dropping pipe are formed using an extrusion moldingtechnology. In another implementation, the pipeline in the heated areaof the fin and the pipeline of the dropping pipe are formed using a blowmolding technology. Compared with a cast fin, a fin manufactured usingthe extrusion molding technology or the blow molding technology islighter and thinner, facilitating development of light and thincommunications products. A manner such as mechanical processing orwelding may alternatively be used for the fin to form the pipeline inthe heated area and the dropping pipe.

With reference to the foregoing implementations, the fin is plate-like.The fin and the base may be perpendicular or basically perpendicular toeach other.

With reference to the foregoing implementations, the fin includes acurved surface, and a curving direction of the curved surface extendsbetween the root and the tip, and the fin vertically extends between thetop and the bottom. In an implementation, the fin has apartially-cylindrical surface or a semi-cylindrical surface, and adesign of the curved surface is conducive to increasing a windward areawithin a same size between the root and the tip, thereby improving aheat dissipation capability. Heat of the fin is usually dissipatedthrough air cooling in a product, and airflow flows over the fin to takeaway the heat. Because the tip is far away from the heat source, atemperature of the tip is lower than that of the root. In other words,temperatures from the root to the tip are distributed in a descendingmanner.

The curved surface is curved and extends in a smooth arc shape. Theextension in the smooth arc shape does not affect mutual communicationbetween the pipelines in the heated area, and the transverse pipeline inthe heated area may also extend in an arc shape. The longitudinalpipelines in the heated area are not affected by the curved surface andstill maintain a vertical tube shape, because the curving direction ofthe curved surface extends between the root and the tip.

With reference to the foregoing implementations, the heat sink furtherincludes a connecting piece, and the connecting piece is connectedbetween tips of two adjacent fins. The two adjacent fins are connectedto each other by disposing the connecting piece. In this way, efficiencycan be improved both in a process of making the fins and in a process ofinstalling the fins onto the base.

Further, a plurality of holes are disposed on the connecting piece. Theholes may be of a shutter structure, or openings may be directlydisposed on the connecting piece. The holes can be disposed not only tohelp decrease a mass of the heat sink, but also help improve a heatdissipation capability, because the holes make space between the fins becommunicated with the outside.

With reference to the foregoing implementations, a quantity of fins istwice a quantity of connecting pieces. A passage is disposed between twoadjacent fins, and two adjacent connecting pieces are isolated by thepassage. In other words, two fins and one connecting piece together forma U-shaped heat dissipation unit, the heat sink includes a plurality ofheat dissipation units, and adjacent heat dissipation units are keptseparated.

The connecting piece and the two adjacent fins form such an integratedstructure. The integrated structure can be more easily made. Forexample, pipeline areas of two independent fins may be directly madeusing the blow molding technology on one plate. The pipeline areas ofthe two independent fins are spaced apart from each other using theconnecting piece, and then the two fins and the connecting piece arebent using a bending technology, to form a U-shaped heat dissipationunit.

In another implementation, the heat sink includes a cover plate. Aposition of the cover plate is the same as a position of the connectingpiece. In other words, the connecting piece is replaced with the coverplate structure. The connecting piece may be considered as a stripstructure between two adjacent fins. The cover plate in thisimplementation may be considered as an overall plate structure. Thecover plate covers a side of tips of all fins, and the cover plate iscombined with the tips of the fins. The cover plate and the tips of thefins may be fastened to each other in a welding or riveting manner, orin a sliding-fit detachable connection manner. For example, a slot maybe disposed on a surface of the cover plate, and the tip is nested intothe slot and cooperates with the slot to implement cooperation betweenthe cover plate and the fin. A structure of the cover plate is similarto a structure of the base. Differences between the two structuresinclude the following: No electronic element is disposed on the coverplate, and the cover plate is configured only to fasten the fin andassist in heat dissipation; in addition to the fin fastened to the base,an electronic element is also disposed on the base. The cover plate maybe disposed in parallel to the base.

In an implementation, a detachable connection structure is used betweenthe root of the fin and the base. For example, a slot is disposed on thebase, and the root is nested into the slot to cooperate with the slot toimplement fastening between the base and the fin.

In another implementation, the root of the fin and the base are fastenedand connected to each other in a shrink-fit, riveting, welding, orgluing manner.

According to a second aspect, the present disclosure further provides acommunications product, including the heat sink and a heat emittingelement, where a side, which backs on a side of the fin, of the base ofthe heat sink is connected to the heat emitting element in a thermallyconductive manner, and the heat emitting element may be directlydisposed on the base.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram of a fin of a heat sink according to anembodiment of the present disclosure.

FIG. 2 is a schematic diagram of a fin of a heat sink according toanother embodiment of the present disclosure.

FIG. 3 is a schematic diagram of a heat dissipation unit including twofins of a heat sink according to an embodiment of the presentdisclosure.

FIG. 4 is a schematic plane view of one end of the heat dissipation unitshown in FIG. 3.

FIG. 5 is a schematic partial view of a cross section of the heatdissipation unit shown in FIG. 4 in an A-A direction.

FIG. 6 is a schematic diagram of a heat sink according to animplementation of the present disclosure.

DESCRIPTION OF EMBODIMENTS

The following describes the embodiments of the present disclosure withreference to the accompanying drawings.

Referring to FIG. 1, FIG. 2, and FIG. 6, a heat sink in an embodiment ofthe present disclosure includes a base 10 and a plurality of fins 20,where the plurality of fins 20 are spaced apart on the base 10 to form acooling fin structure. In an embodiment, the plurality of fins 20 arespaced apart from each other at an equal distance. The base 10 is madeof a thermally conductive material, such as a metal plate or a ceramicbase 10. The base 10 includes two surfaces that are opposite to eachother. One of the two surfaces of the base 10 is configured to get incontact with a heat emitting element in a communications product, andmay be disposed, using thermally conductive adhesive or a thermallyconductive medium, between the base 10 and the heat emitting elementsuch that the base 10 and the heat emitting element are thermally incontact with each other. The other surface of the base 10 is configuredto install the plurality of fins 20.

Referring to FIG. 1 and FIG. 2, each of the fins 20 includes a root 21and a tip 22 that are disposed opposite to each other. Each of the fins20 further includes a top 23 and a bottom 24 that are disposed oppositeto each other and connected between the root 21 and the tip 22. In anembodiment, the fin 20 is in a square or rectangle as a whole, and theroot 21, the tip 22, the top 23, and the bottom 24 are respectivelylocated on four sides of the fin 20. The root 21 is connected to thebase 10. In an embodiment, the fin 20 is erected on a surface of thebase 10 by combining the root 21 and the base 10. The fin 20 and thebase 10 may be perpendicular to each other, or there may be a specifictilt angle between the fin 20 and the base 10. A standard for settingthe tilt angle is to ensure that the tip 22 far away from the base 10reaches a temperature making a working medium in the fin 20 turn from agas state to a liquid state. In an embodiment, the fin 20 is roughly ina rectangular plate shape, the root 21 and the tip 22 are located on twoopposite long sides of the rectangular plate shape, and the top 23 andthe bottom 24 are located on two opposite short sides of the rectangularplate shape.

A heated area 25, a dropping pipe 26, and a spacing strip 27 thatseparates the heated area 25 from the dropping pipe 26 are formed in thefin 20. An area represented by a dashed line box in FIG. 1 or FIG. 2 isthe heated area 25. In a use environment, the root 21 is closest to aheat source, and heat is transferred from the root 21 to other parts ofthe fin 20; therefore, a working medium in the heated area 25 is heatedand starts working first. The heated area 25 is located between the root21 and the spacing strip 27. The dropping pipe 26 is located between thespacing strip 27 and the tip 22. A first passage 28 and a second passage29 are formed between the heated area 25 and the dropping pipe 26. Thefirst passage 28 is located between the spacing strip 27 and the top 23,and the second passage 29 is located between the spacing strip 27 andthe bottom 24. A hydraulic diameter of a pipeline in the heated area 25is less than a critical dimension such that the working medium in theheated area 25 is heated to form a gas-liquid plug flow flowing towardthe first passage 28 and flowing into the dropping pipe 26 through thefirst passage 28. A hydraulic diameter of a pipeline of the droppingpipe 26 is greater than or equal to the critical dimension, and apressure of liquid at an intersection of the second passage 29 and thedropping pipe 26 is greater than a pressure of liquid at an intersectionof the second passage 29 and the heated area 25 such that liquid in thedropping pipe 26 flows toward the heated area 25 through the secondpassage 29. The hydraulic diameter (hydraulic diameter) is a ratio offour times a flow cross-sectional area to a wetted perimeter. Thecritical dimension is a maximum hydraulic diameter of a pipeline thatcan be used when the working medium in the heated area is heated in thepipeline to form a gas-liquid plug flow. In other words, when thehydraulic diameter of the pipeline is greater than the criticaldimension, the working medium heated in the pipeline cannot become inthe gas-liquid plug flow state. A required hydraulic diameter of thepipeline varies according to different working media.

In the present disclosure, the pipeline in the heated area 25 and thedropping pipe 26 are formed in the fin 20, the heated area 25 and thedropping pipe 26 are isolated from each other by the spacing strip 27,and the first passage 28 and the second passage 29 are disposed at twoends of the spacing strip 27 such that the heated area 25 and thedropping pipe 26 are communicated with each other. Because the base 10is close to the heat source, the working medium in the heated area 25 isheated. In addition, because the hydraulic diameter of the pipeline inthe heated area 25 is less than the critical dimension, the workingmedium can form the gas-liquid plug flow after being heated. Air bubblesin the liquid push the liquid to flow toward the first passage 28 at thetop 23. The first passage 28 is equivalent to a transverse flowgathering area at the top 23 of the fin 20. Because the air bubbles inthe heated area 25 rush up, liquid reaching the first passage 28 doesnot flow downward but flows along the first passage 28 into the droppingpipe 26. In the embodiments shown in FIG. 1 and FIG. 2, threeside-by-side first passages 28 are formed between the spacing strip 27and the top 23. Similarly, three side-by-side second passages 29 areformed between the spacing strip 27 and the bottom 24. The pressure ofthe liquid at the intersection of the second passage 29 and the droppingpipe 26 is greater than the pressure of the liquid at the intersectionof the second passage 29 and the heated area 25 such that the liquid inthe dropping pipe 26 flows toward the heated area 25 through the secondpassage 29. In this way, the working medium inside the fin 20 iscirculated from the heated area 25 to the first passage 28, the droppingpipe 26, and the second passage 29, and then back to the heated area 25.

The first passage 28 and the second passage 29 are honeycombed. In anembodiment, the first passage 28 and the second passage 29 each includeat least two crisscrossed pipelines. The pipeline in the heated area 25includes a plurality of longitudinal pipelines that extend from thebottom 24 to the top 23, and a plurality of transverse pipelines thatare communicated between the longitudinal pipelines. The transversepipeline is configured to perform pressure balancing and temperaturebalancing of liquid and vapor. In an embodiment, the longitudinalpipelines extend in a direction from the second passage 29 to the firstpassage 28.

In the present disclosure, working medium circulation also exists insidethe heated area 25. The transverse pipeline is communicated between thelongitudinal pipelines in the heated area 25. When liquid levels of thelongitudinal pipelines are different in height, liquid in a longitudinalpipeline whose liquid level is relatively high flows through thetransverse pipeline into a longitudinal pipeline whose liquid level isrelatively low such that a pressure and a temperature of liquid andvapor in the heated area are balanced.

In the embodiment shown in FIG. 1, the pipelines in the heated area 25are honeycombed, and the heated area 25 is separated by a plurality ofpolygonal (which may be hexagonal, octagonal, or the like) or smallround cake-shaped spacing zones 251 in the heated area 25 to form thepipelines (the pipelines herein are the longitudinal passage and thetransverse passage). In other words, a pipeline is formed between twoadjacent spacing zones 251. The small cake-shaped spacing zones 251 arevertically arranged in two columns, and the two columns of smallcake-shaped spacing zones 251 are interlaced. In a horizontal direction,a pipeline between two spacing zones 251 in one column is exactlydisposed opposite to a pipeline between two spacing zones 251 in theother column. The two columns of spacing zones 251 form threelongitudinal pipelines. In the embodiment shown in FIG. 1, thelongitudinal pipelines are rising pipelines. The longitudinal pipelineextends in a shape of a wave line. A side, adjacent to the heated area25, of the spacing strip 27 is in a shape of a wave line, and a side,adjacent to the dropping pipe 26, of the spacing strip 27 isstraight-lined.

In the embodiment shown in FIG. 2, the heated area 25 is separated by aplurality of bar-shaped spacing zones 252 in the heated area 25 to formthe pipelines. The bar-shaped spacing zone 252 includes twostraight-lined long sides, and the two long sides are connected bycurved sides. The bar-shaped spacing zones 252 are vertically arrangedin two columns, and the transverse pipeline is formed between twoadjacent spacing zones 252 in one column. In the embodiment shown inFIG. 2, the longitudinal pipelines extend as straight-lined pipelines.The spacing strip 27 is also bar-shaped. A shape of the spacing strip 27is similar to a shape of the spacing zone 252. Both the side, adjacentto the heated area 25, of the spacing strip 27 and the side, adjacent tothe dropping pipe 26, of the spacing strip 27 are straight-lined.

There is at least one column of dropping pipes 26. In an implementation,as shown in FIG. 1, there are two or more columns of dropping pipes 26,and adjacent dropping pipes 26 are communicated with each other througha transverse pipeline.

In an implementation, a range of the critical dimension is 0.5 mm to 20mm. Selection of the critical dimension is associated with selection ofthe working medium.

In an implementation, the pipeline in the heated area 25 of the fin 20and the pipeline of the dropping pipe 26 are formed using an extrusionmolding technology. In another implementation, the pipeline in theheated area 25 of the fin 20 and the pipeline of the dropping pipe 26are formed using a blow molding technology. Compared with a cast fin 20,a fin 20 manufactured using the extrusion molding technology or the blowmolding technology is lighter and thinner, facilitating development oflight and thin communications products.

With reference to the foregoing implementations, the fin 20 isplate-like. The fin 20 and the base 10 may be perpendicular or basicallyperpendicular to each other.

In another implementation, the fin 20 may be a non-plate structure, andthe fin 20 includes a curved surface. In an embodiment, a curvingdirection of the curved surface extends between the root 21 and the tip22, and the fin 20 vertically extends between the top 23 and the bottom24. In an implementation, the fin 20 has a partially-cylindrical surfaceor a semi-cylindrical surface, and a design of the curved surface isconducive to increasing a windward area within a same size between theroot 21 and the tip 22, thereby improving a heat dissipation capability.Heat of the fin 20 is usually dissipated through air cooling in aproduct, and airflow flows over the fin 20 to take away the heat.Because the tip 22 is far away from the heat source, a temperature ofthe tip 22 is lower than that of the root 21. In other words,temperatures from the root 21 to the tip 22 are distributed in adescending manner.

The curved surface is curved and extends in a smooth arc shape. Theextension in the smooth arc shape does not affect mutual communicationbetween the pipelines in the heated area 25, and the transverse pipelinein the heated area 25 may also extend in an arc shape. The longitudinalpipelines in the heated area 25 are not affected by the curved surfaceand still maintain a vertical tube shape, because the curving directionof the curved surface extends between the root 21 and the tip 22.

As shown in FIG. 3, FIG. 4, and FIG. 5, with reference to the foregoingimplementations, the heat sink further includes a connecting piece 30,and the connecting piece 30 is connected between tips 22 of two adjacentfins 20. The two adjacent fins 20 are connected to each other bydisposing the connecting piece 30. In this way, efficiency can beimproved both in a process of making the fins 20 and in a process ofinstalling the fins 20 onto the base 10.

Further, a plurality of holes 31 are disposed on the connecting piece30. The holes 31 may be of a shutter structure, or openings may bedirectly disposed on the connecting piece 30. The holes 31 can bedisposed not only to help decrease a mass of the heat sink, but alsohelp improve a heat dissipation capability, because the holes 31 makespace between the fins 20 be communicated with the outside.

With reference to the foregoing implementations, a quantity of fins 20is twice a quantity of connecting pieces 30. A passage is disposedbetween two adjacent fins 20, and two adjacent connecting pieces 30 areisolated by the passage. In other words, two fins 20 and one connectingpiece 30 together form a U-shaped heat dissipation unit, the heat sinkincludes a plurality of heat dissipation units, and adjacent heatdissipation units are kept separated through the passage.

As shown in FIG. 3 to FIG. 6, in an implementation, pipelines of thefins 20 of the heat dissipation unit are formed on an inner side. Inother words, each fin 20 includes two faces. Pipelines are disposed onone face, and the other face is a plane. In each heat dissipation unit,pipelines are disposed on faces that are of one fin 20 and the other fin20 and that are opposite to each other, and the other face of each fin20 is a plane. Such a design makes the pipelines of the heat sink beconcealed in an inner side of space that is formed by a pair of fins 20,the connecting piece 30, and the base 10 such that an appearance of theheat sink is smooth and flat.

The connecting piece 30 and the two adjacent fins 20 form such anintegrated structure. The integrated structure can be more easily made.For example, pipeline areas of two independent fins 20 may be directlymade using the blow molding technology on one plate. The pipeline areasof the two independent fins 20 are spaced apart from each other usingthe connecting piece 30, and then the two fins 20 and the connectingpiece 30 are bent using a bending technology, to form a U-shaped heatdissipation unit.

A detached structure may alternatively be used between the connectingpiece 30 and the two adjacent fins 20, to install the connecting piece30 onto the fins 20 through structural cooperation (for example, using aconnection manner such as welding, gluing, or screw fastening). Theconnecting piece 30 is connected to the fins 20, to ensure structuralstability of the fins 20.

In another implementation, the heat sink includes a cover plate. Aposition of the cover plate is the same as a position of the connectingpiece 30. In other words, the connecting piece 30 is replaced with thecover plate structure. The connecting piece 30 may be considered as astrip structure between two adjacent fins. The cover plate in thisimplementation may be considered as an overall plate structure. Thecover plate covers a side of tips 22 of all fins 20, and the cover plateis combined with the tips 22 of the fins 20. The cover plate and thetips 22 of the fins 20 may be fastened to each other in a welding orriveting manner, or in a sliding-fit detachable connection manner. Forexample, a slot may be disposed on a surface of the cover plate, and thetip 22 is nested into the slot and cooperates with the slot to implementcooperation between the cover plate and the fin 20. A structure of thecover plate is similar to a structure of the base 10. Differencesbetween the two structures include the following: No electronic elementis disposed on the cover plate, and the cover plate is configured onlyto fasten the fin and assist in heat dissipation; in addition to the fin20 fastened to the base, an electronic element is also disposed on thebase 10. In other words, the base 10 may be a circuit board on which anelectronic element and a connection interface are disposed, and the heatemitting element is disposed on a side, which backs on a side of the fin20, of the base 10. The cover plate may be disposed in parallel to thebase 10.

In an implementation, a detachable connection structure is used betweenthe root 21 of the fin 20 and the base 10. For example, a slot isdisposed on the base 10, and the root 21 is nested into the slot tocooperate with the slot to implement fastening between the base 10 andthe fin 20.

In another implementation, the root 21 of the fin 20 and the base 10 arefastened and connected to each other in a welding or gluing manner.

The present disclosure further provides a communications product,including the heat sink and a heat emitting element. A side, which backson a side of the fin 20, of the base 10 of the heat sink is connected tothe heat emitting element in a thermally conductive manner. The heatemitting element and the base 10 may be fit using a thermally conductivemedium, or may be directly in contact with each other. A position of theheat emitting element on the base 10 is exactly opposite to a middlearea between the top 23 and the bottom 24 of the fin 20.

In the present disclosure, a size of the pipeline in the heated area ofthe heat sink is restricted, that is, the hydraulic diameter of thepipeline in the heated area is less than the critical dimension suchthat the working medium in the heated area is heated to form thegas-liquid plug flow. In addition, a size of a pipeline of the droppingpipe is restricted. In other words, the hydraulic diameter of thedropping pipe is greater than or equal to the critical dimension. Inthis way, self-circulation is formed inside the fin of the heat sinksuch that the gas-liquid plug flow drives more liquid working media toparticipate in heat exchange, thereby improving heat dissipationefficiency and avoiding a case that the liquid working media staying inthe bottom of the heat sink do not participate in the heat exchange.

On a basis of improving the heat dissipation efficiency, compared with aheat sink in the prior art, the heat sink provided in the presentdisclosure can implement a same amount of dissipated heat, with only arelatively small size and volume.

What is claimed is:
 1. A heat sink, comprising: a base; and a pluralityof fins disposed on the base to form a cooling fin structure, whereineach of the plurality of fins comprises: a root connected to the base; atip located on a side opposite to the base; a heated area locatedbetween the root and a spacing strip; a dropping pipe located betweenthe spacing strip and the tip, wherein the spacing strip separates theheated area from the dropping pipe in the fin, a first passage; and asecond passage, wherein the first passage and the second passage areformed between the heated area and the dropping pipe, wherein the heatedarea is configured to heat a working medium in the heated area to form agas-liquid plug flow flowing toward the first passage and into thedropping pipe through the first passage, and wherein the heat sink isconfigured by configuring a hydraulic diameter of a pipeline in theheated area and a hydraulic diameter of a pipeline of the dropping pipeaccording to a critical dimension, wherein the critical dimension is amaximum hydraulic diameter of a pipeline that can be used when theworking medium in the heated area is heated in the pipeline to form thegas-liquid plug flow, so that a pressure of liquid at an intersection ofthe second passage and the dropping pipe is greater than a pressure ofliquid at an intersection of the second passage and the heated area suchthat liquid in the dropping pipe flows toward the heated area throughthe second passage when the working medium is heated.
 2. The heat sinkaccording to claim 1, wherein the pipeline in the heated area comprisesa plurality of longitudinal pipelines and a transverse pipeline that isdisposed between the plurality of longitudinal pipelines, wherein thelongitudinal pipelines extend in a direction from the second passage tothe first passage, and wherein the transverse pipeline is configured toperform pressure balancing and temperature balancing of liquid andvapor.
 3. The heat sink according to claim 2, wherein the heated areacomprises a plurality of spacing zones, and wherein each of the spacingzones separates the heated area to form the longitudinal pipelines andthe transverse pipeline.
 4. The heat sink according to claim 3, whereinthe plurality of spacing zones are arranged in two columns, and whereinthe two columns of spacing zones are interlaced and form threelongitudinal pipelines.
 5. The heat sink according to claim 3, whereinthe plurality of spacing zones are in a shape of a polygon or circle. 6.The heat sink according to claim 3, wherein each of the pluralityspacing zones is bar-shaped, wherein each of the plurality of spacingzones comprises two straight-lined long sides, wherein the twostraight-lined long sides are connected by curved sides, wherein theplurality of spacing zones are arranged in two adjacent columns, whereina longitudinal pipeline is formed between the two adjacent columns ofthe plurality of spacing zones, and wherein the transverse pipeline isformed between two adjacent spacing zones in one column.
 7. The heatsink according to claim 2, wherein each of the longitudinal pipelinesextend in a shape of a wave line.
 8. The heat sink according to claim 1,wherein a side adjacent to the heated area of the spacing strip is in ashape of a wave line, and wherein a side adjacent to the dropping pipeof the spacing strip is straight-lined.
 9. The heat sink according toclaim 1, wherein both a side adjacent to the heated area of the spacingstrip and a side adjacent to the dropping pipe of the spacing strip arestraight-lined.
 10. The heat sink according to claim 1, furthercomprising at least one column of dropping pipes, and wherein at leastone column of dropping pipes are in two adjacent columns communicatedwith each other through a transverse pipeline.
 11. The heat sinkaccording to claim 1, wherein the first passage is honeycombed, andwherein the first passage comprises at least two crisscrossed pipelines.12. The heat sink according to claim 1, wherein a range of the criticaldimension is between 0.5 millimeters (mm) to 20 mm.
 13. The heat sinkaccording to claim 1, wherein the fin is structured as a plate.
 14. Theheat sink according to claim 1, further comprising a connecting piececonnecting tips of two adjacent fins.
 15. The heat sink according toclaim 14, wherein a plurality of holes are disposed on the connectingpiece.
 16. The heat sink according to claim 14, wherein a quantity ofthe plurality fins is twice a quantity of connecting pieces.
 17. Theheat sink according to claim 16, wherein a passage is disposed betweentwo adjacent fins, and wherein two adjacent connecting pieces areisolated by the passage.
 18. The heat sink according to claim 1, furthercomprising a cover plate, wherein the plurality of fins are fastenedbetween the cover plate and the base.
 19. The heat sink according toclaim 18, wherein the base is a circuit board, and wherein a heatemitting element is disposed on a side opposite of the fins.
 20. Acommunications product, comprising: a heat emitting element, and heat ofthe heat emitting element is conducted from a side, which backs on aside of the fin, of the base of the heat sink to the base; and a heatsink, comprising: a base; and a plurality of fins disposed on the baseto form a cooling fin structure, wherein each of the plurality of finscomprises: a root connected to the base; and a tip located on a sideopposite to the base; a heated area located between the root and aspacing strip; a dropping pipe located between the spacing strip and thetip, wherein the spacing strip separates the heated area from thedropping pipe in the fin; a first passage; and a second passage, whereinthe first passage and the second passage are formed between the heatedarea and the dropping pipe, wherein the heated area is configure to heata working medium in the heated area to form a gas-liquid plug flowflowing toward the first passage and into the dropping pipe through thefirst passage, and wherein the heat sink is configured by configuring ahydraulic diameter of a pipeline in the heated area and a hydraulicdiameter of a pipeline of the dropping pipe according to a criticaldimension, wherein the critical dimension is a maximum hydraulicdiameter of a pipeline that can be used when the working medium in theheated area is heated in the pipeline to form the gas-liquid plug flow,so that a pressure of liquid at an intersection of the second passageand the dropping pipe is greater than a pressure of liquid at anintersection of the second passage and the heated area such that liquidin the dropping pipe flows toward the heated area through the secondpassage when the working medium is heated.